ages = {
    'Tom': 18,
    'Jack': 19,
    'Alex': 17
}

# 遍历的是所有Key
for item in ages:
    print(item)

for key in ages.keys():
    print(key, ages[key])

for value in ages.values():
    print(value)

for item in ages.items():
    print(item)

for key, value in ages.items():
    print(key, value)
